1. Field of the Invention
The present invention relates to a zero level setting circuit for an A/D converter in a magnetic disk drive, and more particularly, the present invention relates to a zero level setting circuit in a signal processing system of a magnetic disk drive for improving the dynamic range of an A/D converter in the signal processing system to process the read signal in a digital state.
2. Description of the Related Art
In recent years, with the increase in speed of computer systems, external storage units such as magnetic disk drives are required to have more speed and capacity. A magnetic disk drive must be equipped with a demodulator capable of handling signals of high frequency and must have high recording density. These requirements are factors which deteriorate the quality of signals. It is necessary, therefore, to improve not only a system relating to a head and a medium of the magnetic disk drive but also the demodulator of the read signal from the disk so that it can demodulate low-quality signals. For this purpose, a digital demodulating system has been proposed.
The digital demodulating system employs an A/D converter for converting an input read signal into a digital signal. To improve conversion accuracy, the A/D converter must employ many bits.
The number of bits of the A/D converter, however, must be as small as possible in terms of circuit scale, power consumption, and heat generation. Accordingly, it is required to provide an A/D converter that can achieve maximum conversion accuracy with a small number of bits.